how do I load a file for c++ on mac

Question

I am trying to load my file with C++ using ifstream, however it just wouldn't work. I use Atom with Xcode as compiler on my Mac.

This pops up:

dyn3180-214:~ joshua$ /var/folders/y6/jrfdjlsx0nqcxyfvsrfw6bnw0000gn/T/excersice ; exit;
file was not opened correctly
logout

#include <iostream>
#include <fstream>
#include <cstdlib>

int main(){
  std::ifstream infile;
  infile.open("numbers.txt");
  if(!infile.is_open()){
    std::cout<<"file was not opened correctly"<<std::endl;
    exit(EXIT_FAILURE);
  }
  int n;
  while(infile>>n){
    std::cout<<n<<std::endl;
  }
  return 0;
}

Are you running your executable at the directory the file is located in? — StoryTeller - Unslander Monica, Jan 07 '19 at 06:18
Assuming you have required read permission, you can use absolute path or make sure your current directory contains the required file. If you have write permissions to the directory, an ofstream would generate a file in this directory. — Gyapti Jain, Jan 07 '19 at 06:21
@StoryTeller Yes, I am running my .cpp file in the same folder as the .txt file. — joshl9688, Jan 07 '19 at 06:31
@AlanBirtles on the terminal this shows up: dyn3180-214:~ joshua$ /var/folders/y6/jrfdjlsx0nqcxyfvsrfw6bnw0000gn/T/excersice ; exit; file was not opened correctly logout — joshl9688, Jan 07 '19 at 06:35
How are you running your program? Presumably from xcode? What have you set the working directory to? — Alan Birtles, Jan 07 '19 at 06:38
@AlanBirtles Yes, I run it form Xcode, and I haven't changed the working directory yet, is that why? — joshl9688, Jan 07 '19 at 06:42
Yes, i can't remember what the default is but as your code isn't working it obviously isn't the directory containing your text file — Alan Birtles, Jan 07 '19 at 07:11
@AlanBirtles I tried to go on Xcode and go to File>Workspace Setting, but and change it to my file containing the .cpp and .txt, but somehow I still can't load my file.. — joshl9688, Jan 07 '19 at 07:16
I still don't understand why students are not told to compile on the command line. IDEs are always confusing them. But that is not OP's fault. — Basile Starynkevitch, Jan 07 '19 at 07:24
see https://stackoverflow.com/questions/3396378/change-the-working-directory-in-xcode — Alan Birtles, Jan 07 '19 at 07:43

Basile Starynkevitch · Answer 1 · 2019-01-07T07:22:19.927

Read how to debug small programs and also the documentation of GDB (or of whatever debugger you have on your machine).

Compile your program (that is the C++ file, let's name it josh.cc, shown in your question) with all warnings and debug info. I recommend to compile it on the command line with g++ -Wall -Wextra -g josh.cc -o joshprog (read how to invoke GCC for details) then to debug it with gdb ./joshprog and to run it in a terminal as ./joshprog.

The point is that your IDE (Atom + XCode) is not helping you. It hides you important details (see this answer, it also works for MacOSX or other Unix systems). That is why I strongly recommend compiling (and running, and debugging) your code with explicit commands that you are typing in a terminal emulator for your shell and understanding (so read the documentation of every command that you are using). Once you are fluent with compilation on Unix systems, you might eventually switch to an IDE (but you need to understand what your IDE is doing on your behalf, and what commands it is running).

You could add into your code something displaying the current working directory by using getcwd (which requires #include <unistd.h> on POSIX system), maybe something like

char mycwdbuf[80];
memset (mycwdbuf, 0, sizeof(mycwdbuf));
if (getcwd(mycwdbuf, sizeof(mycwdbuf)-1) != NULL)
   std::cout << "current directory is " << mycwdbuf << std::endl;

By doing that, you'll probably understand how is your program started and in which working directory. I guess that it was not started in the working directory that you wanted it to.

Sekin · Answer 2 · 2021-08-26T22:45:50.617

In Xcode, select the project navigator, then click on your project. This will open the project editor. Select the Build Phases tab. Open the dropdown for Copy Files. Set Destination to Products Directory. Add a Subpath if you have to. Drag the necessary files into the project editor or add them via +.

Example: During the build phase, project files associated with the target will be copied to the designated subpath in the directory within the Products directory.

score -1 · Answer 3 · answered Jan 07 '19 at 06:55

-1

I think, Xcode generating the .o (object file ) file in different directory, and your .txt is present in different directory. I do code in Xcode, it always generate the .o file in different directory.

answered Jan 07 '19 at 06:55

Vipul Sharma

42
2

where should I move my .txt file to? I can't seem to find it. – joshl9688 Jan 07 '19 at 06:57
1

One easy way, compile your program through terminal it will create object file in the same directory. – Vipul Sharma Jan 07 '19 at 08:15

how do I load a file for c++ on mac

3 Answers3